Back to EveryPatent.com
United States Patent |
5,632,372
|
Steinbuchel, IV
,   et al.
|
May 27, 1997
|
Conveyor tensioning assembly
Abstract
A conveyor tensioning assembly for an article conveyor is mounted to the
frame of the article conveyor, and connected to a take-up sprocket. The
conveyor tensioning assembly includes a movable rack that is engaged and
moved by an advancing gear of an advancing and holding assembly in a first
direction, causing the take-up sprocket of the article conveyor to be
urged outwardly against the conveyor chain of the article conveyor so as
to take-up any slack existing within the conveyor chain and place the
conveyor chain under tension. Once the conveyor chain has been tensioned,
the rack is engaged by a holding gear mounted on a one-way clutch, which
prevents the holding gear from rotating in a counter-clockwise direction.
The holding gear retards in any rearward movement of the rack so as to
resist slippage and/or backlash of the rack to prevent the chain from
losing tension and slack being formed therein to maintain the conveyor
chain under a substantially constant tension.
Inventors:
|
Steinbuchel, IV; Herman J. (Marietta, GA);
Brown; Steven (Canton, GA)
|
Assignee:
|
Riverwood International Corporation (Atlanta, GA)
|
Appl. No.:
|
576074 |
Filed:
|
December 21, 1995 |
Current U.S. Class: |
198/813 |
Intern'l Class: |
B65G 023/44 |
Field of Search: |
198/813,814,815
|
References Cited
U.S. Patent Documents
2612988 | Oct., 1952 | Andrews | 198/814.
|
2893255 | Jul., 1959 | Bayliss | 198/814.
|
3599506 | Aug., 1971 | Freese | 198/813.
|
3687274 | Aug., 1972 | Clark et al. | 198/813.
|
4995506 | Feb., 1991 | Langenbacher et al. | 198/814.
|
5156260 | Oct., 1992 | Dorner et al. | 198/813.
|
Primary Examiner: Dayoan; D. Glenn
Claims
Wherefore, the following is claimed:
1. A tensioning assembly for an article conveyor having a conveyor chain
passing about a series of sprockets, said tensioning assembly comprising:
a rack;
means for moving said rack in a first direction, said means for moving said
rack being positioned adjacent the rack and including a cylinder assembly
mounted adjacent said rack and an advancing member connected to said
cylinder assembly and engaging said rack so that as said cylinder assembly
moves said advancing member in said first direction said advancing member
urges said rack in said first direction:
said advancing member including an advancing gear mounted on a one-way
clutch so as to be rotatable in one direction while resisting rotation in
an opposite direction;
a carrier mounted to a first end of said rack so as to move with said rack
and having a take-up sprocket attached thereto for the conveyor chain such
that said take-up sprocket is moved with the movement of said rack to take
up slack from the conveyor chain; and
holding means mounted along said rack adjacent said means for moving and
having a one-way clutch, said holding means adapted to engage said rack
and enable said rack to move in said first direction to remove slack from
the conveyor chain while retarding movement of said rack in an opposite
direction to prevent backlash and slippage of the conveyor chain.
2. The tensioning assembly of claim 1, said cylinder assembly further
including a pair of pneumatic cylinders.
3. The tensioning assembly of claim 1 and further comprising a sensor
positioned along said rack adjacent said means for moving said rack for
detecting a second end of said rack indicating stretch of the conveyor
chain.
4. The tensioning assembly of claim 1 and further comprising a support
slide mounted above said carrier and along which said carrier is supported
and moves to move said take-up sprocket outwardly to a tensioning
position.
5. The tensioning assembly of claim 1 and wherein said holding means
comprises a holding gear mounted on a one-way clutch so as to be rotatable
in one direction while being held against rotation in an opposite
direction, said holding gear rotatably engaging said rack to enable
movement of said rack in said first direction while resisting movement of
said rack in said opposite direction to prevent slipping of the conveyor
chain and the forming of slack in the conveyor chain.
6. In an article conveyor system of the type having a frame, a series of
sprockets mounted about the frame and a conveyor chain extended about the
sprockets and rotated along a conveying path, the improvement therein
comprising:
a movable rack mounted to the system frame and connected to a take-up
sprocket for the conveyor chain for moving said take-up sprocket outwardly
to tension the conveyor chain;
means for moving said rack in a first direction for moving said take-up
sprocket to a tensioning position to enable adjustment of the tension in
the conveyor chain, said means for moving said rack including a cylinder
assembly mounted adjacent said rack and an advancing member connected to
said cylinder assembly and engaging said rack so that as said cylinder
assembly moves said advancing member in said first direction, said
advancing member urges said rack in said first direction;
said advancing member including an advancing gear mounted on a one-way
clutch so as to be rotatable in one direction while resisting rotation in
an opposite direction; and
means for securing said rack against movement in a second direction
opposite said first direction, said means for securing being positioned
along and in engagement with said rack, said means for securing including
a clutch constructed and arranged to resist movement of said rack in said
second direction while permitting movement of said rack in said first
direction to retard backlash of said rack and maintain the conveyor chain
under tension.
7. The system of claim 6 and wherein said clutch comprises a holding gear
mounted on a one-way clutch so as to rotate in one direction while being
held against rotation in an opposite direction, said holding gear
rotatably engaging said rack to enable movement of said rack in said first
direction while resisting movement of said rack in said second direction
to prevent slipping of the conveyor chain and the forming of slack in the
conveyor chain.
8. The system of claim 6 and further including a release means for
disengaging both said means for moving said rack and said clutch from said
rack to enable said rack to be moved in said second direction to a
retracted position.
9. The system of claim 6 and wherein said advancing member further includes
a slide plate to which said advancing gear is mounted, said slide plate
being mounted to said cylinder assembly so as to be movable in said first
and said second directions by said cylinder assembly.
10. The system of claim 6 and further including a series of sensors mounted
at spaced intervals along said rack for detecting said rack at varying
positions to provide varying amounts of tension in said conveyor chain.
11. In an article conveyor system of the type having a frame, a series of
sprockets mounted about the frame and a conveyor chain extended about the
sprockets and rotated along a conveying path, the improvement therein
comprising:
a movable rack mounted to the system frame and connected to a take-up
sprocket for the conveyor chain for moving said take-up sprocket outwardly
to tension the conveyor chain:
means for moving said rack in a first direction for moving said take-up
sprocket to a tensioning position to enable adjustment of the tension in
the conveyor chain;
means for securing said rack against movement in a second direction
opposite said first direction, said means for securing being positioned
along and in engagement with said rack and including a clutch constructed
and arranged to resist movement of said rack in said second direction
while permitting movement of said rack in said first direction to retard
backlash of said rack and maintain the conveyor chain under tension; and
a sensor positioned along said rack in a position for detecting a second
end of said rack indicating tensioning of the conveyor chain.
12. A method of tensioning a conveyor chain to remove slack therefrom, said
method comprising the steps of:
actuating a cylinder assembly;
engaging and moving a rack in a first direction with an advancing member so
as to move a take-up sprocket outwardly;
tensioning the conveyor chain until the tension in the chain substantially
balances the force of the cylinder assembly moving the take-up sprocket
outwardly; and
providing an advancing gear mounted on a one-way clutch rotatable in said
first direction only, and rotating said advancing gear on said rack as
said rack is moved in said first direction so as to enable the rack to
move in said first direction while resisting movement of the rack in an
opposite direction once the conveyor chain has been tensioned to prevent
backlash of the rack and the forming of slack therein.
13. A method of tensioning a conveyor chain to remove slack therefrom, said
method comprising the steps of:
actuating a cylinder assembly;
engaging and moving a rack in a first direction with an advancing member so
as to move a take-up sprocket outwardly by moving an advancing gear in
said first direction in response to the actuation of the cylinder
assembly, said advancing gear engaging and urging the rack in said first
direction;
tensioning the conveyor chain until the tension in the chain substantially
balances the force of the cylinder assembly moving the take-up sprocket
outwardly; and
providing a clutch means that engages and rotates as the rack is moved in
said first direction to enable the rack to move in said first direction
while resisting movement of the rack in an opposite direction once the
conveyor chain has been tensioned to prevent backlash of the rack and the
forming of slack therein.
14. The method of claim 13 and wherein the step of actuating said cylinder
assembly includes the step of pulsing an air cylinder for a desired time.
15. The method of claim 13 and further including the steps of disengaging
the clutch means from the rack and moving the rack in a second direction
to reset the rack to an initial retracted position in response thereto.
Description
FIELD OF THE INVENTION
The present invention relates to a tensioning assembly for removing slack
from a conveyor chain. In particular, the present invention relates to a
conveyor tensioning assembly which includes an advancing gear and a
holding gear both mounted on one way clutches and engaging a rack so that
as the advancing gear is moved forwardly in a first direction, the rack is
urged longitudinally to move a take-up sprocket of the conveyor chain of
the conveyor to a tensioning position. After the rack has been moved to
its tensioning position by the advancing gear, the rack is engaged and
held by the holding gear which is restricted from rotating in a reverse
direction by its one-way clutch mounting to prevent backlash or movement
of the rack in a rearward direction, which would cause the chain to loosen
and slack to be formed therein.
BACKGROUND OF THE INVENTION
In automated operations for the production of goods, such as during the
manufacture and packaging of goods, the goods, packaging materials, etc.
generally are conveyed along a processing or packaging path on an article
conveyor. Such article conveyors typically include a conveyor belt or
chain extended about a series of sprockets or rollers in a substantially
endless loop. It is important that the conveyor chain or belt be under
tension and have no slack therein as the chain is revolved around its
conveying path. If slack is present in the conveyor chain, the chain
potentially can slip or jump out of engagement with the teeth of the
conveyor sprockets, especially where there is a limited engagement between
the chain and the drive sprockets of the conveyor. Such jumping or
slippage poses a significant danger to the operation of the packaging
equipment, potentially disrupting the operation of the equipment or
causing misfeeding of the articles, and thus damaging of the articles
being conveyed. Overtensioning of the conveyor chain, however, leads to
increased wear and reduced life of the conveyor chain, and requiring more
often, costly replacement of the conveyor chain. Additionally, as space
constraints in plants have increased, requiring reductions in the size of
automated production and packaging equipment and article conveyors, the
amount of engagement of the conveyor chains with the teeth of their drive
and idler sprockets has decreased, increasing the chances of slippage or
jumping of the conveyor chains.
To remedy the problems of loose or slack conveyor chains, chain tensioning
or take-up devices have been developed for tensioning or taking up the
slack of conveyor chains. Typically, such take-up mechanisms have included
a ratchet and pawl mechanism that generally comprise a horizontally
extending rack, one end of which is connected to a take-up sprocket for
the conveyor chain, and a means for moving the rack and take-up sprocket
longitudinally to tension and remove slack from the conveyor chain. The
rack has a series of teeth formed along its upper edge and which are
engaged by a spring loaded pawl as the rack is moved longitudinally. The
pawl permits the rack to be moved in a first direction to move the take-up
sprocket outwardly to take up any slack existing in the conveyor chain,
while generally preventing significant rearward movement of the rack.
An example of such a conventional conveyor take-up or tensioning assembly
is illustrated in U.S. Pat. No. 5,038,919 of Harston. The Harston patent
generally discloses a conveyor system formed with two parallel, endless
chains that carry transversely spaced flights. The conveyor assembly of
Harston further includes spring loaded pawls that engage a ratchet bar,
forming part of an adjustment means for adjusting the tension in the
conveyor chain. An air cylinder is pressurized periodically to pull guide
blocks, which support the conveyor chains and about which the conveyor
chains are passed, outwardly to increase the tension in the conveyor
chains. The engagement of the ratchet bar by the spring loaded pawls is
designed to hold the tension in the conveyor chains.
The problem with such conventional take-up assemblies generally is that the
tension in the conveyor chain can only be adjusted in discreet steps
corresponding to the size of the teeth of the rack. Thus, if the rack is
stopped with the pawl halfway between a pair of teeth of the rack, the
rack will tend to slip back, commonly referred to as backlash, until the
pawl engages a previous tooth recess of the rack. As a result, the
conveyor chain at times will be slack when the pawl has slipped back to a
previous tooth recess, and at other times will be under tension instead of
a consistent tension being maintained on the conveyor chain during its
operation.
Accordingly, it can be seen that a need exists for a conveyor tensioning
assembly that enables the fine adjustment of tension in a conveyor chain
without requiring such adjustment to be performed in finite, discreet
steps and in which the potential for backlash of the conveyor chain is
avoided to insure that a substantially constant tension is maintained in
the conveyor chain.
SUMMARY OF THE INVENTION
Briefly described, the present invention comprises a conveyor tensioning
assembly for removing slack from and tensioning a belt or chain of an
article conveyor assembly. Typically, the article conveyor includes an
elongated, looped chain or belt extended about a series of conveyor
sprockets mounted upon a frame. One of the conveyor sprockets functions as
a drive sprocket which is rotated to cause the conveyor chain to revolve
about the sprockets along a substantially endless looped conveying path.
The conveyor tensioning assembly is mounted to the frame of the article
conveyor and is connected to a take-up sprocket of the article conveyor
for moving the take-up sprocket outwardly to take up any slack in the
conveyor chain and place the conveyor chain under tension.
The conveyor tensioning assembly includes a housing mounted to the article
conveyor frame and through which a rack is extended, with the rack
supported upon and movable along a base pivotally mounted to the housing.
The rack generally is an elongated bar formed from a metal such as steel
or similar material having a first end, a second end, a flat lower surface
that moves along the base, and an upper surface having a series of teeth
or serrations formed therein between the first and second ends of the
rack. A take-up sprocket for the conveyor chain is connected to the first
end of the rack so as to be movable therewith. The rack is movable
forwardly in a first direction, substantially parallel to a lower run of
the article conveyor to move the take-up sprocket outwardly to take-up
existing slack in the conveyor chain and to tension the chain, and is
further movable rearwardly in a second direction, opposite its first
direction, for lessening the tension in the chain of the article conveyor.
An advancing means is mounted within the housing, positioned above and
engaging the rack for moving the rack longitudinally in its first
direction. The advancing means generally includes a pair of pneumatic
cylinders aligned horizontally, with each cylinder including a piston rod,
that is extensible in a direction substantially parallel to the first
direction of movement of the rack. The cylinders typically are pulsed for
approximately two to ten seconds at a time during normal tensioning
operation. The force of the cylinders is sufficient to take up any slack
in the chain of the article conveyor assembly, but is insufficient to
stretch or over-tension the chain past its maximum limit once the chain
has been fully tensioned by the conveyor tensioning assembly.
A slide block is positioned within the housing, attached to the free ends
of the piston rods of the air cylinders and supported on rollers mounted
within the housing so as to be movable with the extension and retraction
of the piston rods. The slide block is attached to the free ends of the
piston rods of the air cylinders by fasteners such as bolts, etc. An
advancing gear having a series of teeth formed about its circumference,
which teeth engage the teeth of the rack, is mounted within the slide
block by a one-way clutch. The one-way clutch enables the advancing gear
to be rotated so that the teeth move in the direction of the advancing
rack, but prevents the reverse rotation of the advancing gear in the
direction of the retracting rack. The slide block and advancing gear are
moved forwardly in their first direction by the extension of the piston
rods of the cylinders. As the slide block and advancing gear are moved
forwardly, the teeth of the advancing gear engage the teeth of the rack,
with the advancing gear held against rotation by its one-way clutch, to
cause the rack to be urged and moved with the advancing gear and slide
block forwardly in its first direction.
A holding means is positioned adjacent the advance gear in engagement with
the rack. The holding means generally includes a holding gear mounted on a
one way clutch so as to be rotatable in the direction of the advancing
rack only and having a series of teeth formed about its circumference. The
teeth of the holding gear engage and mesh with the teeth of the rack. The
holding gear accordingly is rotated in the direction of the advancing rack
with the movement of the rack in its first direction by the movement of
the advancing gear. When the advancing gear's movement is stopped, the
holding gear is locked against rotation in the reverse direction by its
one way clutch while the advancing gear is moved rearwardly back to an
initial position by the retraction of the piston rods into their
cylinders. As a result, the rack, with its teeth in meshing engagement
with the teeth of the holding gear, and the take-up sprocket mounted to
the first end of the rack are secured in a tensioning position, and
rearward movement, or backlash, of the rack in a second direction,
opposite its first direction, is retarded to avoid any lessening of
tension or the formation of slack within the chain of the article
conveyor. Such a locking arrangement avoids potential backlash by the
rack, that could cause the chain to be loosened or slackened, especially
if the chain was tensioned by air alone.
A carrier is mounted to the first end of the rack so as to move
longitudinally with the movement of the rack. The carrier generally
includes a pair of spaced carrier plates attached to one another and
supported from and movable along a slide means mounted to the frame of the
article conveyor. The take-up sprocket of the article conveyor is mounted
between and supported by the carrier plates adjacent the first or
forwardmost ends thereof. Thus, as the rack is moved forwardly in its
first direction by the movement of the advance gear by the pneumatic
cylinders of the tensioning assembly, the take-up sprocket likewise is
carried forwardly to take up any slack existing within the conveyor chain
and place the conveyor chain under tension.
Additionally, a sensor means is mounted to the base support for the rack,
positioned along the length of the rack. The sensor means generally
comprises an induction type proximity sensor positioned so as to detect
the second or trailing end of the rack as the rack is moved longitudinally
forward in its first direction. Upon detection of the second or trailing
end of the rack, the sensor sends a signal to the machine control to
advise the operator that the conveyor chain has been substantially
stretched approximately to its maximum limit to prevent possible damage to
the chain from being run in a condition stretched beyond pitch limits.
Various objects, features and advantages of the present invention will
become apparent to those skilled in the art upon reading the following
specification, when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view, with portions broken away, of the
article conveyor having the conveyor tensioning assembly of the present
invention mounted thereto.
FIG. 2 is a plan view of the housing conveyor tensioning assembly, taken in
partial cross section along lines 2--2 of FIG. 3A, illustrating the
construction of the housing and advancing means.
FIGS. 3A-3B are side elevational views, taken in partial cross section,
illustrating the operation of the conveyor tensioning assembly of the
present invention.
FIG. 4 is a side elevational view schematically illustrating the resetting
of the rack to its initial position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now in greater detail to the drawings in which like numerals
indicate like parts throughout the several views, FIG. 1 illustrates an
article conveyor 10 to which the conveyor tensioning assembly 11 of the
present invention is mounted. The article conveyor includes an elongated,
substantially rectangular conveyor frame 12 having a first end 13, a
second end 14 and upper and lower sections 16 and 17. A series of
sprockets 18-22 are rotatably mounted to the frame at the comers between
the first and second ends 13 and 14 and the upper and lower sections 16
and 17 of the frame 12. Each of the sprockets is a circular plate or gear
having a series of teeth 23 formed about its circumference. The teeth of
the sprockets engage a conveyor chain 24 to hold the conveyor chain about
the conveyor frame 12. Sprocket 21, positioned along the lower section of
the frame 12 adjacent the second end 14 is connected to a drive motor or
similar means for rotating the sprocket so that the sprocket 21 functions
as a drive sprocket for driving a conveyor chain 24 of the article
conveyor about a substantially looped conveying path illustrated by arrows
26.
As illustrated in FIG. 1, the conveyor chain 24 generally is a
substantially endless-looped chain formed from a series of chain links 27.
The conveyor chain 24 is extended about the sprockets 18-22, with the
teeth 23 of the sprockets engaging the chain links to hold and move the
conveyor chain along its conveying path 26. The conveyor chain moves along
its conveying path 26 in the direction of arrows A and A' along an upper
run 28 that extends parallel to the upper section 16 of the conveyor frame
12 and a lower run 29 that extends parallel to the lower section 17 of the
frame 12. The articles to be conveyed, such as bottles, soft drink cans,
etc. are supported on the conveyor chain and are moved along the upper run
28 thereof along the conveying path 26 with the movement of the conveyor
chain by its drive sprocket 21 to convey the articles through a processing
station such as a packaging machine or similar equipment.
As FIG. 1 further illustrates, the conveyor tensioning assembly 11 is
mounted to the frame 12 of the article conveyor 10 adjacent its first or
forwardmost end 13. The conveyor tensioning assembly includes a housing 35
that mounts to the conveyor frame. The housing is formed from a pair of
spaced, substantially rectangularly shaped plates 36 oriented vertically
and extending substantially parallel to one another, as illustrated in
FIG. 2. The plates each include forward and rearward ends 38 and 39, and
upper and lower edges 41 and 42 (FIG. 3A). Cut outs or clearance openings
43 and 44 are formed in the housing plates 36 at intermediate positions
between the forward and rearward ends thereof. Each cut-out is a
substantially rectangular shaped opening, with the cut-outs of each plate
aligned with one another. As illustrated in FIG. 3A, a pair of rollers 46
are mounted to the housing plates, positioned between the upper edges 41
of the housing plates 36 and the upper edge of the forward most cut-outs
43.
A base 50 is mounted to the lower edges 42 of the housing plates 36 of the
housing 35 and positioned within the space. The base generally is a
substantially rectangular-shaped beam or member having a rearward end 51
and a forward end 52 and is received and positioned within the space
between the opposed, parallel plates of the housing along their lower
edges. As illustrated in FIG. 4, the rearward ends 39 of the housing
plates are pivotally attached to the base by a pivot pin 53, while the
forwardmost ends 38 of the housing plates are releasably attached to the
first or forward end 52 of the base 50 by a locking assembly 54. The
locking assembly typically includes a spring loaded button 56 or catch
that, when in its extended locking position, locks the plates of the
housing securely to the base. As the button 56 of the locking assembly 54
is depressed, it disengages the connection between the housing plates and
the base to enable the housing to be pivoted upwardly in the direction of
arrows B about the pivot pin 53. In the alternative, the locking assembly
54 can comprise a shoulder pin manually inserted through aligned openings
formed adjacent the forward end 52 of the base 50 and through the plates
of the housing to lock the housing plates and the base together and which
releases the housing from engagement with the base when the pin is
removed.
The conveyor tensioning assembly 11 further includes a rack 60 that is
received between and is movable along the length of the housing plates 36,
supported on the base 50. The rack generally is an elongated beam formed
from steel or similar durable metal material and has a series of
serrations or teeth 61 formed along its length between the ends 62 and 63
of the rack. The rack teeth can either be triangular or rectangular or any
other desired configuration and are formed with recesses 64 therebetween.
As shown in FIGS. 3A and 3B, rollers 66 and 67 are mounted at spaced
positions along the length of the base. The rack is supported on the
rollers 66 and 67 of the base 50 so as to be movable in the direction of
arrows A and A', substantially parallel to the conveying path 24 (see FIG.
1) for the conveyor chain 23.
FIGS. 3A-3C illustrate an advancing and holding assembly 70 for moving the
rack 60 in the direction of arrow A and locking the rack in a set,
tensioning position as illustrated in FIG. 3B. The advancing and holding
assembly 70 generally includes a cylinder assembly 71, typically including
a pair of pneumatic cylinders 72 and 73 mounted within the second or
rearmost cutout or clearance openings 44 of the housing 35. The cylinders
are positioned one above the other in a vertically stacked, parallel
extending arrangement, and typically are of the same pressure, sufficient
to take-up any slack and place the conveyor chain approximately under its
maximum tension, but which is insufficient to stretch the chain past its
maximum tension to avoid stretching or overtensioning the chain. In
addition, different pressure cylinders can be used as desired for varying
the force applied to the chain to account for changing geometry of the
chain during the course of tensioning over the life of the chain, and for
adjusting the maximum amount of tension applied by the conveyor tensioning
assembly 11. The cylinders 72 and 73 are actuated in a pulse or burst of
approximately 2 to 10 seconds, and each includes an extensible piston rod
74. The piston rods and cylinders are extensible in the direction of
arrows A upon actuation of the cylinders, and are retracted in an opposite
direction, indicated by arrows A', upon deactivation of the cylinders.
The free ends 76 of the piston rods 74 are attached to and support a slide
block 77 of the advancing and holding assembly 70. The slide block
generally is a substantially rectangular shaped block formed from a metal
such as aluminum or steel, or other durable, rigid material that is
attached to the free ends of the piston rods so as to be movable in the
direction of arrows A and A' with the extension and retraction of the
piston rods as shown in FIGS. 3A and 3B. The upper edge of the slide block
engages and rolls on the first pair of rollers 46 mounted along the upper
edge 41 of the housing as it is moved back and forth in the direction of
arrows A and A' by the cylinders 72 and 73.
As illustrated in FIGS. 2-4, an advancing gear 78 is mounted within the
slide block 77. The advancing gear comprises a disk having a series of
spaced teeth 79 formed about its circumference, which teeth are adapted to
engage and mesh with the teeth 61 (FIGS. 3A and 3B) of the rack 60. The
advancing gear is mounted on a one way clutch 81 that enables the rotation
of the advancing gear in a clockwise direction, as indicated by arrow B,
while blocking any rotation in the opposite, counterclockwise direction.
Thus, as the slide block and advancing gear are moved forwardly in the
direction of arrows A by the pulsing of the cylinders 72 and 73, the one
way clutch 81 of the advancing gear holds the advancing gear against
rotation as the teeth 79 of the advancing gear engage the teeth 61 of the
rack 60, causing the rack to be urged in the direction of arrow A as shown
in FIG. 3A.
Once the cylinders of the cylinder assembly have been deactuated and the
piston rods 74 thereof are retracted in the direction of arrow A' (FIG.
3B), the slide block is pulled rearwardly in the direction of arrow A'
with the retraction of the piston rods 74. The advancing gear also is
retracted, rolling along the length of the rack and rotating in the
direction of arrow B by its one-way clutch as the slide block and
advancing gear are reset to their initial position illustrated in FIG. 3B.
Generally, the amount of travel of the slide block per stroke of the
piston rods of the cylinders 72 and 73 is approximately 10 millimeters,
although the lesser or greater movement or stroke can be provided if so
desired. As a result, the rack is moved a discrete amount up to a maximum
of approximately 10 millimeters per cycle.
A holding means 82 of the advancing and holding assembly 70 is mounted
within the housing 35 forwardly of the slide block 77 and advancing gear
78. The holding means generally comprises a holding gear 83 having
radially extending teeth 84 formed about its circumference. The holding
gear 83 is mounted adjacent the forward end 38 of the housing 35 with its
teeth 84 in meshing engagement with the teeth 61 of the rack 60. The
holding gear is mounted on a one way clutch 86 that enables the rotation
of the holding gear in a clockwise direction, indicated by arrow C, while
restricting the rotation of the holding gear in an opposite,
counterclockwise direction. As a result, as indicated in FIG. 3A, as the
rack is moved in the direction of arrow A with the forward movement of the
slide block and advancing gear by the extension of the piston rod 74 of
the cylinder 72 and 73, the holding gear is rotated in the direction of
arrow C, permitting the rack to move freely forward. As the cylinders 72
and 73 thereafter are deactuated and their piston rods 74 are retracted in
the direction of arrow A' (FIG. 3B), the holding gear is locked in place
by its one way clutch mounting 86. Thus, the rack, with its teeth in
meshing engagement with the teeth 84 of the holding gear 83, is locked in
place by the holding gear and rearward movement of the rack in the
direction of arrow A' is prevented. Additionally, the position of the
holding gear within the housing 35 can be adjusted vertically with respect
to the rack to permit a certain amount of clearance or slack to be
retained in the chain if so desired. Such adjustment is accomplished by
moving the holding gear vertically away from the rack so that the teeth of
the holding gear only partially engage the teeth of the rack to create a
slight clearance between the teeth of the rack and the teeth of the
holding gear for the running of the conveyor chain with a slight built in
clearance.
As illustrated in FIGS. 1-4, a carrier 90 is mounted to the first or
forwardmost end 62 of the rack 60, connected thereto by a bracket assembly
91. The bracket assembly 91 (FIG. 2) includes a substantially Z-shaped
bracket plate 92 having a first end 93 and a second end 94. The first end
93 attaches to the forwardmost end 62 of the rack by a pin 96 or similar
fastener inserted through the rack and first end 93 of the bracket plate
92 and secured therewith by bushings 97. The carrier 90 (FIGS. 1, 3A and
3B) itself is formed from a pair of spaced, parallel plates 98 and 99
attached together along their length by fasteners 101, such as screws or
similar fasteners. Carder plate 98 has a substantially L-shaped
configuration, including a vertically extending rearward portion 102 to
which the bracket plate 92 of the bracket assembly 91 is attached by
fasteners 103 such as screws, bolts, or the like. Carrier plate 99 is a
generally rectangular shaped plate having substantially the same
configuration as the lower portion of carrier plate 98 and is mounted
thereto.
The upwardly extending rear portion 102 of carrier plate 98 is mounted to a
slide assembly 105 which supports the carrier 90 as it is urged forwardly
by the movement of the rack in the direction of arrow A. The slide
assembly includes a pair of vertically spaced slide bars 106 and 107 that
extend horizontally along the length of the conveyor frame 12 (FIG. 1),
parallel to the upper run 28 of the conveyor chain 24. Slide mountings 108
are attached to the upper end of the rear portion 102 of carrier plate 98
and are slidably mounted between the slide bars so as to slide along the
length of the slide bars to support the carrier therefrom as the rack
moves the carrier in the direction of arrow A. The slide mountings
typically comprise reciprocating ball mountings although other types of
movable or adjustable mounting means can be used as well.
As shown in FIG. 1, the carrier 90 is attached at its forwardmost end to
sprocket 22 of the article conveyor 10. The sprocket 21 functions as a
take-up sprocket for taking up or removing slack from the conveyor chain
24 extended thereabout. The take-up sprocket 22 is mounted between the
forward or first end 109 of the carrier plates 98 and 99, sandwiched
therebetween. The take-up sprocket 22 is mounted to the carrier plate by
an axle or pivot pin 111 so as to enable the take-up sprocket to rotate as
the conveyor chain is pulled thereabout. The take-up sprocket 22 is moved
in the direction of arrow A by the actuation of the cylinders of the
advancing and holding assembly, which cause the slide block and advancing
gear and thus the rack with its teeth in meshing engagement with the
advancing gear, to be moved forwardly so as to urge the carrier in the
direction of arrow A. As the carrier is moved outwardly, the take-up
sprocket 22 mounted thereto moves against the conveyor chain, causing the
conveyor chain to be placed under tension as slack is removed therefrom.
As shown in FIGS. 1 and 3A-4, a sensor 115 is mounted to the second or rear
end 116 of the base 50. The sensor typically is an induction type sensor
or similar detecting means that is directed upwardly toward the rack 60.
The sensor detects the absence of the ferrous metal of the rack such as
when the second or rearmost end 63 of the rack 60 has been moved past the
rearward end 51 of the base 50 and the sensor 115. Upon detection of the
movement of the second or rear end of the rack past the sensor, the sensor
sends a signal to the control system for the article conveyor indicating
that the conveyor chain has been stretched or tensioned to approximately
its maximum limit.
It is further possible to use additional sensors 116 and 117 (shown in
phantom in FIG. 1) mounted at spaced intervals upstream from a sensor 115
to detect the rearmost end 63 of the rack at different positions to detect
the movement of the rack to selected positions as desired to provide
varying amounts or degrees of tension within the conveyor chain. Further,
the cylinders of the advancing and holding assembly further can be of
different pressure capacities or sizes so as to vary the amount of take up
or tension that is placed on the conveyor chain, working in conjunction
with the several sensors 115-117 to provide greater control of the amount
of tension applied to the chain. In such an arrangement, the cylinders can
be actuated independently of each other to provide first and second levels
of tensioning, and both can be actuated to provide a third or maximum
tensioning of the conveyor chain as desired to account for varying chain
geometry during the stroke of the takeup sprocket.
OPERATION
In the operation of the conveyor tensioning assembly 10 (FIGS. 1, 3A-4),
for removing the slack from a conveyor chain and placing the conveyor
chain under tension as it is moved about an article conveyor 10 (FIG. 1)
along a conveying path, the rack 60 initially is in its retracted position
as shown in FIGS. 1 and 3A. Thereafter, the cylinders 72 and 73 of
cylinder assembly 71 of the advancing and holding assembly 70 are actuated
for a pulse or cycle of between approximately 2 to 10 seconds. In
response, the cylinders extend their piston rods 74 in the direction of
arrows A, causing the slide block and advancing gear 78 to be moved
forwardly in the direction of arrows A with the teeth 79 of the advancing
gear in meshing engagement with the teeth 61 of the rack 60. The rack
accordingly also is moved forwardly in the direction of arrow A by the
forward movement of the slide block and advancing gear. As the rack is
moved forwardly, the carrier is urged along the slide assembly, carrying
the take-up roller 22 therewith. As the take-up roller is moved with the
carrier in the direction of arrow A, it pushes against the conveyor chain
so that the conveyor chain is tensioned so as to take up and remove any
slack existing therein.
At the end of a pulse or cycle, the cylinders are deactuated, causing the
piston rods of the cylinders to be retracted in the direction of arrow A'
(FIG. 3B). As the piston rods of the cylinders are retracted, the slide
block and advancing gear are likewise pulled rearwardly in the direction
of arrow A', with the advancing gear rotating in a clockwise direction as
indicated by arrow B as it rolls along the length of the rack. The
advancing gear and slide block are retracted to their initial, retracted
position shown in FIG. 3A to await an additional tensioning operation. At
the same time, the teeth of the rack are engaged by the teeth 84 of
holding gear 83, which is prevented from rotating in a counterclockwise
direction, which would enable the rack to be moved rearwardly in the
direction of arrow A', by the one way clutch 86 that mounts the holding
gear to the housing 35. Thus, the rack is fixed in place so as to resist
backlash or slippage of the rack rearwardly, which would cause an
undesirable lessening of the tension in the conveyor chain.
During an initial tensioning operation, at the initial start up of the
article conveyor, the slide block and advancing gear are moved along the
full stroke of the cylinder, approximately 10 millimeters, during the
pulse of the cylinders. The actuation of the cylinder assembly is
repeated, again causing the rack and carrier, and thus the take up
sprocket, to be moved forwardly in the direction of arrow A to continue to
take up any slack remaining in the chain and place the chain under
tension. The amount of travel or cycle of the piston rods of the cylinders
becomes limited as the tension in the conveyor chain reaches its maximum
limit. The force of the cylinders is insufficient to overcome the maximum
tension of the conveyor chain such that as the tension is reached, the
force of the cylinders becomes substantially balanced by the tension in
the conveyor chain to prevent the continued stretching or tensioning of
the chain. Thereafter, the conveyor tensioning assembly is deactivated. In
use generally, the conveyor tensioning assembly is actuated periodically,
such as during the daily start-up of the article conveyor, to take-up
slack formed in the conveyor chain during use.
Over time, as the conveyor chain is subjected to wear and stress, etc.
during operation, it will tend to loosen and slack will form therein. As
slack is formed within the chain, and for example during the start-up of
the article conveyor each morning, the conveyor tensioning assembly 11 is
actuated prior to the placement of articles on the conveyor to provide a
quick adjustment of the tension within the article conveyor at the start
of a conveying operation. Additionally, once it has been detected that the
chain has worn or stretched to its maximum limit, as when the movement of
the second or rearmost end of the rack passes the sensor 115, a signal is
sent to the system control for the article conveyor to indicate that the
chain has been stretched to its maximum limit.
It accordingly can be seen that the present invention provides a quick,
accurate and secure adjustment of the tension within a conveyor chain for
an article conveyor with a significant degree of precision, which enables
the conveyor chain to be substantially precisely stretched to a desired
tension and maintained at such desired tension with danger of backlash
and/or slippage, and thus the formation of slack in the chain, being
minimized. The present invention further can be installed on new article
conveyors or as a retrofit assembly for existing article conveyors for
taking up and maintaining tension within the conveyor chains of the
article conveyors.
Accordingly, it will be understood by those skilled in the art that while
the invention has been disclosed with reference to a preferred embodiment,
various advantages and modifications can be made to the invention without
departing from the spirit and scope of the invention as set forth in the
following claims.
Top